Problem: Khan.scratchpad.disable(); Michael sells magazine subscriptions and earns $$9$ for every new subscriber he signs up. Michael also earns a $$40$ weekly bonus regardless of how many magazine subscriptions he sells. If Michael wants to earn at least $$78$ this week, what is the minimum number of subscriptions he needs to sell?
Answer: To solve this, let's set up an expression to show how much money Michael will make. Amount earned this week $=$ $ $ Subscriptions sold $\times$ Price per subscription $+$ Weekly bonus Since Michael wants to make at least $$78$ this week, we can turn this into an inequality. Amount earned this week $\geq $78$ Subscriptions sold $\times$ Price per subscription $+$ Weekly bonus $\geq $78$ We are solving for the number of subscriptions sold, so let subscriptions sold be represented by the variable $x$ We can now plug in: $x \cdot $9 + $40 \geq $78$ $ x \cdot $9 \geq $78 - $40 $ $ x \cdot $9 \geq $38 $ $x \geq \dfrac{38}{9} \approx 4.22$ Since Michael cannot sell parts of subscriptions, we round $4.22$ up to $5$ Michael must sell at least 5 subscriptions this week.